Temperature surveys in oil-exploratory wells indicate that the geothermal profile underlying the Floridan Plateau is modified anomalously to a negative geothermal gradient (i.e., the ground water becomes colder) to a depth of about 3,000 ft below sea level. The anomaly is related to cold ocean water below the thermocline in the Gulf of Mexico and the Florida Straits. At 3,000 ft below sea level the ground water has a temperature of about 70°F near the edge of the deep sea water bodies, and warms to more than 108°F toward the central axis of the Floridan Plateau. The horizontal and vertical temperature distributions suggest the possibility that cold, dense sea water flows inland through the cavernous dolomite in the deep part of the aquifer where it progressively becomes heated by upward geothermal heat flow. The reduction in density produces an upward convective circulation which brings the sea water into contact with fresh water recharged through sinkholes in the karst region of central Florida. The mixing with fresh water further reduces the density and the diluted salt water then flows seaward and discharges by upward leakage through confining beds into shallow aquifers and thence back to the sea or by discharge through submarine springs on the continental shelf and slope.

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